Transmission arrangement for a vehicle

ABSTRACT

A transmission arrangement for a vehicle includes a first, a second, a third, and a fourth planetary gear set including a sun gear, a planet carrier and a ring gear, respectively, wherein the transmission arrangement further includes a transmission housing, an input shaft and an output shaft, wherein the ring gear of the first planetary gear set and the input shaft are operatively connected to each other; the sun gear of the first planetary gear set, and the sun gear of the second planetary gear set are operatively connected to each other; the planet carrier of the second planetary gear set and the ring gear of the third planetary gear set are operatively connected to each other; the planet carrier of the third planetary gear set is operatively connected to the transmission housing; the sun gear of the third planetary gear set and the sun gear of the fourth planetary gear set are operatively connected to each other; and the planet carrier of the fourth planetary gear set and the output shaft are operatively connected to each other.

BACKGROUND AND SUMMARY

The present invention relates to a transmission arrangement for avehicle. The invention also relates to a vehicle comprising such atransmission arrangement. The invention is applicable on vehicles, inparticularly working machines such as e.g. wheel loaders, articulatedhaulers, dump trucks, etc. Although the invention will mainly bedescribed in relation to an articulated hauler, it may also beapplicable for other types of vehicles such as e.g. trucks.

In connection with transportation of heavy loads at construction sitesor the like, a working machine is often used. The working machines maybe utilized for transportations in connection with road or tunnelbuilding, sand pits, mines, forestry and similar environments. Thus, theworking machine is frequently operated with large and heavy loads inrough terrain and on slippery ground where no regular roads are present.

In order to fulfil the desired demands from the fields where the workingmachine is frequently operated, high performance of the vehicle gearboxis necessary. The gearbox is arranged for adjusting the speed andtractive effort of the vehicle in dependency of the specific drivingscenario. The gearbox comprises a transmission arrangement and dependingon the specific type of gearbox, the transmission arrangement maycomprise e.g. ordinary gear sets with cylindrical gear wheels in meshedconnection with each other or planetary gear sets comprising arespective sun gear, ring gear and a planet carrier, or a combination ofordinary gear sets and one or more planetary gear sets.

SE 527 108 describes a vehicle transmission arrangement, particularlysuitable for working machines. The transmission arrangement in SE 527108 comprises an input shaft and an output shaft. Five planetary gearsets are arranged between the input shaft and the output shaft forproviding the desired gear ratios. Also, the transmission arrangementcomprises three clutches and five brakes for achieving the desired gearshifts. Hereby, nine forward gears and four reverse gears are providedfor the transmission arrangement in. SE 527 108.

Although the transmission arrangement in SE 527 108 provides for asufficient number of gears, the transmission arrangement is still inneed of further improvements in terms of costs and functionality.

It is desirable to provide a transmission arrangement that enables fewercomponents to be used and has an improved gear shiftability incomparison to the prior art.

According to a first aspect of the present invention, there is provideda transmission arrangement for a vehicle, the transmission arrangementcomprising a first, a second, a third, and a fourth planetary gear setcomprising a sun gear, a planet carrier and a ring gear, respectively,wherein the transmission arrangement further comprises a transmissionlousing an input shaft and an output shaft, wherein the ring gear of thefirst planetary gear set and the input shaft are operatively connectedto each other; the sun gear of the first planetary gear set and the sungear of the second planetary gear set are operatively connected to eachother; the planet carrier of the second planetary gear set and the ringgear of the third planetary gear set are operatively connected to eachother; the planet carrier of the third planetary gear set is operativelyconnected to the transmission housing, the sun gear of the thirdplanetary gear set and the sun gear of the fourth planetary gear set areoperatively connected to each other; and the planet carrier of thefourth planetary gear set and the output shaft are operatively connectedto each other.

The wording “operatively connected to” should in the following andthroughout the entire description be interpreted such that thecomponents thereof are fixedly connected to each other, i.e. therotational speeds of the components which are operatively connected toeach other are equal. Hence, no engagement and disengagement mechanismor the like is arranged between the components that are operativelyconnected to each other and they can therefore not be disengaged fromone another during operation. Accordingly, the planet carrier of thefourth planetary gear set is always connected to the output shaft of thetransmission arrangement.

An advantage of the present invention is that, in comparison to theprior an, only four planetary gear sets are used in order to obtain asufficient number of forward and reverse gears. This is advantageousboth in terms of cost and packaging of the transmission arrangementsince the number of components reduces the total cost for thetransmission arrangement at the same time as it will be easier to fitthe transmission arrangement to a vehicle. The engine compartment is anenvironment where it often is desirable to reduce the size of thecomponents housed therein and the present invention hence reduces thesize of the transmission arrangement by having one less planetary gearset in comparison to the prior art.

Moreover, by means of the present invention, nine forward gears andthree reverse gears are obtainable, where the ratios and the steps forthe different gears are considered to be able to appropriately operatee.g. a working machine to provide sufficient speed when necessary andsufficient torque when necessary. The ratio and step for the differentobtainable gears will be described further below in relation to thedetailed description of the present invention.

A still further advantage is that further additional gears andalternative gears in addition to the nine forward gears and the threereverse gears described above are obtainable. These additional gears andalternative gears will also be described further below in relation tothe detailed description of the present invention.

According to an example embodiment, the transmission arrangement maycomprise a first connecting mechanism for selectively connecting thering gear of the second planetary gear set to the ring gear of the firstplanetary gear set and to the input shaft. The first connectingmechanism may, for example, be a clutch arrangement, such as e.g. a wetor dry friction disc clutch. Other alternatives are also conceivable,such as a dog clutch.

The wording “selectively connectable to” should be understood to meanthat the components thereof are connectable to each other such that,when being connected to each other, the components have equal rotationalspeeds. Hence, the components may be directly connectable to each otheror via another component.

According to an example embodiment, the transmission arrangement maycomprise a second connecting mechanism for selectively connecting theplanet carrier of the first planetary gear set to the output shaft andto the planet carrier of the fourth planetary gear set. The secondconnecting mechanism may, for example, be a clutch arrangement, such ase.g. a wet or dry friction disc clutch. Other alternatives are of coursealso conceivable.

According to an example embodiment, the transmission arrangement maycomprise a third connecting mechanism for selectively connecting thering, gear of the fourth planetary gear set to the sun gear of the firstplanetary gear set and to the sun gear of the second planetary gear set.The third connecting mechanism may, for example, be a clutcharrangement, such as e.g. a wet or dry friction disc clutch. Otheralternatives are of course also conceivable.

According to an example embodiment, the transmission arrangement maycomprise a fourth connecting mechanism for selectively connecting theplanet carrier of the first planetary gear set to the ring gear of thefourth planetary gear set. The fourth connecting mechanism may, firexample, be a clutch arrangement, such as e.g. a wet or dry frictiondisc clutch. Other alternatives are of course also conceivable.

According to an example embodiment, the transmission arrangement maycomprise a first locking mechanism for selectively locking the ring gearof the fourth planetary gear set to the transmission housing. The firstlocking mechanism may, or example, be a brake arrangement, such as e.g.a wet or dry friction disc brake. Other alternatives are alsoconceivable such as a dog clutch.

According to an example embodiment, the ring gear of the fourthplanetary gear set may be selectively connectable to the transmissionhousing via the planet carrier of the third planetary gear set.

Accordingly, since the planet carrier of the third planetary gear set isoperatively connected to the transmission housing, the ring gear of thefourth planetary gear set can hence be locked to the transmissionhousing via the planet carrier of the third planetary gear set such thatthe ring gear of the fourth planetary gear set is prevented fromrotating.

According to an example embodiment, the transmission arrangement maycomprise a second locking mechanism for selectively locking the sun gearof the third planetary gear set and the sun gear of the fourth planetarygear set to the transmission housing. The second locking mechanism may,for example, be a brake arrangement, such as e.g. a wet or dry frictiondisc brake. Other alternatives are of course also conceivable.

According to an example embodiment, the sun gear of the third planetarygear set and the sun gear of the fourth planetary gear set may beselectively connectable to the transmission housing via the planetcarrier of the third planetary gear set.

Accordingly, since the planet carrier of the third planetary gear set isoperatively connected to the transmission housing, the sun gear of thethird planetary gear set and the sun gear of the fourth planetary gearset can hence be locked to the planet carrier of the third planetarygear set fin: preventing rotation of the sun gear of the third planetarygear set and the sun gear of the fourth planetary gear set.

According to an example embodiment, the transmission arrangement maycomprise a third locking mechanism for selectively locking the ring gearof the second planetary gear set to the transmission housing. The thirdlocking mechanism may, for example, be a brake arrangement, such as e.g.a wet or dry friction disc brake. Other alternatives are of course alsoconceivable.

Hereby, the ring gear of the second planetary gear set can hence belocked to the transmission housing such that the ring gear is preventedfrom rotating.

According to an example embodiment, the stationary gear ratio of eachone of the first, second, third and fourth planetary gear sets may benegative. An advantage is that single planet wheels are used, whichreduces cost and gear mesh losses.

According to a second aspect of the present invention there is provideda method for controlling a transmission arrangement, the transmissionarrangement comprising a first, a second, a third, and a fourthplanetary gear set comprising a sun gear, a planet carrier and a ringgear, respectively, wherein the transmission arrangement furthercomprises a transmission housing, an input shaft and an output shaft;the ring gear of the first planetary gear set being operativelyconnected to the input shaft; the sun gear of the first planetary'gearset being operatively connected to the sun gear of the second planetarygear set; the planet carrier of the second planetary gear set beingoperatively connected to the ring gear of the third planetary gear set;the planet carrier of the third planetary gear set being operativelyconnected to the transmission housing; the sun gear of the thirdplanetary gear set being operatively connected to the sun gear of thefourth planetary gear set; the planet carrier of the fourth planetarygear set being operatively connected to the output shaft, wherein thetransmission arrangement further comprises: a first connecting mechanismfor selectively connecting the ring gear of the second planetary gearset to the ring gear of the first planetary gear set and to the inputshaft; a second connecting mechanism for selectively connecting theplanet carrier of the first planetary gear set to the output shaft andto the planet carrier of the fourth planetary gear set; a thirdconnecting mechanism for selectively connecting the ring gear of thefourth planetary gear set to the sun gear of the first planetary gearset and to the sun gear of the second planetary gear set; a fourthconnecting mechanism for selectively connecting the planet carrier ofthe first planetary gear set to the ring gear of the fourth planetarygear set, a first locking mechanism for selectively locking the ringgear of the fourth planetary gear set to the transmission housing; asecond locking mechanism for selectively locking the sun gear of thethird planetary gear set and the sun gear of the fourth planetary gearset to the transmission housing; and a third locking mechanism forselectively locking the ring gear of the second planetary gear set tothe transmission housing, wherein fear at least one of the gears of thetransmission arrangement, the method comprises the steps of: positioningthree of the locking and connecting mechanisms in an engaged state; andpositioning four of the locking and connecting mechanisms in adisengaged state.

Hereby, the majority of elements are disengaged for the different gearsof the transmission arrangement, which thus may increase durability offriction components etc.

According to an example embodiment, the method may comprise the step ofpositioning the first and the third locking mechanisms, and the secondconnecting mechanism in an engaged state when engaging a first forwardgear. According to an example embodiment, the method may comprise thestep of positioning the first and the third locking mechanisms, and thefourth connecting mechanism in an engaged state when engaging a secondforward gear. According to an example embodiment, the method maycomprise the step of positioning the third locking mechanism, and thesecond and the fourth connecting mechanisms in an engaged state whenengaging a third forward gear. According to an example embodiment, themethod may comprise the step of positioning the second and the thirdlocking mechanisms, and the fourth connecting mechanism in an engagedstate when engaging a fourth forward gear. According to an exampleembodiment, the method may comprise the step of positioning the thirdlocking mechanism, and the third and the fourth connecting mechanisms inan engaged state when engaging a fifth forward gear. According to anexample embodiment, the method may comprise the step of positioning thesecond locking mechanism, and the third and the fourth connectingmechanisms in an engaged state when engaging a sixth forward gear.According to an example embodiment, the method may comprise the step ofpositioning the second, the third and the fourth connecting mechanismsin an engaged state when engaging a seventh forward gear. According toan example embodiment, the method may comprise the step of positioningthe second locking mechanism, and the second and the third connectingmechanisms in an engaged, state when engaging an eighth forward gear.According to an example embodiment, the method may comprise the step ofpositioning the third locking mechanism, and the second and the thirdconnecting mechanisms in an engaged state when engaging a ninth forwardgear.

Thus, well defined forward gears are provided for the transmissionarrangement.

According to an example embodiment, the method may comprise the step ofpositioning the first locking mechanism, and the first and the secondconnecting mechanisms in an engaged state when engaging a first reversegear; According to an example embodiment, the method may comprise thestep of positioning the first locking mechanism, and the first and thefourth connecting mechanisms in an engaged state when engaging a secondreverse gear. According to an example embodiment, the method maycomprise the step of positioning the first locking mechanism, and thefirst and the third connecting mechanisms in an engaged state whenengaging a third reverse gear.

Thus, well defined reverse gears are provided for the transmissionarrangement. All one-step gear shifts as well as all two-step gearshifts for the forward gears and the reverse gears are performed by onlyshifting one of the connecting and locking mechanisms from an engagedstate to a disengaged state, and only shifting one of the connecting andlocking mechanisms from a disengaged state to an engaged state.

According to an example embodiment, the method may comprise the step ofpositioning the second and the third locking mechanisms, and the secondconnecting mechanism in an engaged state when engaging a firstadditional forward gear having a gear ratio between the gear ratios ofthe fifth and the sixth forward gears.

Hereby, a further gear is arranged between the fifth and sixth forwardgears which provides for an additional step between the fifth and sixthgears. A gear shift can be executed from the fourth forward gear to thefirst additional forward gear. This will provide for a smaller step incomparison to a gear shift from the fourth forward gear to the sixthforward gear. Further, when executing a gear shift from the fourthforward gear to the first additional forward gear only one of theconnecting and locking mechanisms are changed from an engaged state to adisengaged state, and only one of the connecting and locking mechanismsare changed from a disengaged state to an engaged state. Still further,the first additional forward gear has high gear mesh efficiency.

According to an example embodiment, the method may comprise the step ofpositioning the first, second and third connecting mechanisms in anengaged state when engaging a second additional forward gear having agear ratio lower than the gear ratio of the ninth forward gear.

Hereby, an additional gear is provided which can increase the vehiclespeed even further in, comparison to the ninth forward gear. Anadvantage is thus that the vehicle may be able to drive at a fasterspeed in situations where this is desirable.

According to an example embodiment, the method may comprise the step ofpositioning the first, second and fourth connecting mechanisms in anengaged state when engaging a first additional reverse gear having agear ratio between the second and the third reverse gears.

According to an example embodiment, the method may comprise the step ofpositioning the second locking mechanism, and the first and the fourthconnecting mechanisms in an engaged state when engaging a secondadditional reverse gear having a gear ratio between the second and thethird reverse gears.

According to an example embodiment, the method may comprise the step ofpositioning the second locking mechanism, and the first and the secondconnecting mechanisms in an engaged state when engaging a thirdadditional reverse gear having a gear ratio lower than the gear ratio ofthe third reverse gear in terms of absolute values.

Hereby, three additional reverse gears are obtained. It has beenrealized that the third reverse gear can be removed when providing thethree additional reverse gears which, thus provides five reverse gearsfor the transmission arrangement. These five reverse gears havebeneficial steps and all one-step gear shifts as well as all two-stepgear shifts are performed by only shifting one of the connecting andlocking mechanisms from an engaged state to a disengaged state, and onlyshifting one of the connecting and locking mechanisms from a disengagedstate to an engaged state.

Also, the third additional reverse gear enables for a further increasedreverse vehicle speed. Hence, the vehicle is able to reverse at a fasterspeed if desired.

It should be readily understood that the above defined exampleembodiments of forward and reverse gears may be combined in any suitablecombination.

Further effects and features of the second aspect of the presentinvention are largely analogous to those described above in relation tothe first aspect of the present invention.

According to a third aspect of the present invention there is provided acontrol unit configured to control a transmission arrangement, thetransmission arrangement comprising a first, a second, a third, and afourth planetary gear set comprising a sun gear, a planet carrier and, aring gear, respectively, wherein said transmission arrangement furthercomprises a transmission housing, an input shaft and n output shaft,wherein the ring gear of the first planetary gear set being operativelyconnected to the input shaft; the sun gear of the first planetary gearset being operatively connected to the sun gear of the second planetarygear set; the planet carrier of the second planetary gear set beingoperatively connected to the ring gear of the third planetary gear set;the planet carrier of the third planetary gear set being operativelyconnected to the transmission housing the sun gear of the thirdplanetary gear set being operatively connected to the sun gear of thefourth planetary gear set; the planet carrier of the fourth planetarygear set being operatively connected to the output shaft, wherein thetransmission arrangement further comprises a first connecting mechanismfor selectively connecting the ring gear of the second planetary gearset to the ring gear of the first planetary gear set and to the inputshaft; a second connecting mechanism for selectively connecting theplanet carrier of the first planetary gear set to the output shaft andto the planet carrier of the fourth planetary gear set; a thirdconnecting mechanism for selectively connecting the ring gear of thefourth planetary gear set to the sun gear of the first planetary gearset and to the sun gear of the second planetary gear set; a fourthconnecting mechanism for selectively connecting the planet carrier ofthe first planetary gear set to the ring gear of the fourth planetarygear set; a first locking mechanism for selectively locking the ringgear of the fourth planetary gear set to the transmission housing; asecond locking mechanism for selectively locking the sun gear of thethird planetary gear set and the sun gear of the fourth planetary gearset to the transmission housing; and a third locking mechanism forselectively locking the ring gear of the second planetary gear set tothe transmission housing, wherein for at least one of the gears of thetransmission arrangement, the control unit is configured to positionthree of the locking and connecting mechanisms in an engaged state; andposition four of the locking and connecting mechanisms in a disengagedstate.

Effects and features of the third aspect of the present invention arelargely analogous to those described above in relation to the first andsecond aspects of the present invention.

According to a fourth aspect of the present invention there is provideda vehicle comprising a prime mover and a gearbox, wherein the gearboxcomprises a transmission arrangement according to any one of theembodiments described above in relation to the first aspect of thepresent invention.

Effects and features of the fourth aspect of the present invention arelargely analogous to those described above in relation to the first,second and third aspects of the present invention.

Further features of, and advantages with, the present invention willbecome apparent when studying the appended claims and the followingdescription. The skilled person realize that different features of thepresent invention may be combined to create embodiments other than thosedescribed in the following, without departing from the scope of thepresent invention.

Definitions

The relationship between the rotational speeds of the different membersin a planetary gear set is defined according to the following:

$\begin{matrix}{\frac{\omega_{S} - \omega_{P}}{\omega_{R} - \omega_{P}} = R} & \left( {{Eq}.\mspace{14mu} 1} \right)\end{matrix}$wherein

-   ω_(S) is the speed of rotation of the sun gear;-   ω_(P) is the speed of rotation of the planet carrier;-   ω_(R) is the speed of rotation of the ring gear; and-   R is the stationary gear ratio of the planetary gear set.    As used herein, the expression “stationary gear ratio” R for a    planetary war set is defined as the ratio of the speed of rotation    of the sun gear to the speed of rotation of the ring gear in a    situation in which the planet carrier is stationary, i.e.:

$\begin{matrix}{{R = {{- \frac{z_{R}}{z_{S}}}\mspace{14mu}{for}\mspace{14mu}{single}\mspace{14mu}{planet}\mspace{14mu}{gear}\mspace{14mu}{wheels}}}{and}} & \left( {{Eq}.\mspace{14mu} 2} \right) \\{R = {{+ \frac{z_{R}}{z_{S}}}\mspace{14mu}{for}\mspace{14mu}{double}\mspace{14mu}{planet}\mspace{14mu}{gear}\mspace{14mu}{wheels}}} & \left( {{Eq}.\mspace{14mu} 3} \right)\end{matrix}$wherein

-   z_(R) is the number of teeth of the ring gear; and-   Z_(S) is the number of teeth of the sun gear.

In a similar manner, the expression “ratio” for a transmissionarrangement should be understood to relate to the number of revolutionsof the input shaft of the transmission arrangement divided by the numberof revolutions of the output shaft of the transmission arrangement.Furthermore, the expression “step” should be understood to mean thequotient achieved when the ratio of a gear is divided by the ratio of anadjacent gear of a transmission arrangement.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as additional features and advantages of the presentinvention, will be better understood through the following illustrativeand non-limiting detailed description of exemplary embodiments of thepresent invention, wherein:

FIG. 1 is a lateral side view illustrating a working machine in the formof an articulated hauler; and

FIG. 2 schematically illustrates a transmission arrangement according toan example embodiment of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown. The invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided forthoroughness and completeness. Like reference character refer to likeelements throughout the description.

FIG. 1 is a side view of a working machine 201 in the form of anarticulated hauler having a tractor unit 202 with a cab 203 for a driverand a trailer unit 204 with a platform having a dump body 205, here inthe form of a container, arranged thereon, for receiving load. The dumpbody 205 is preferably pivotally connected to the rear section andtiltable by means of a pair of tilting cylinders 206, for examplehydraulic cylinders. The tractor unit 202 has a frame 207 and a pair ofwheels 208 suspended from the frame 207. The trailer unit 204 has aframe 209 and two pair of wheels 210, 211 suspended from the frame 209.

The working machine is frame-steered, i.e. there is a joint arrangement212 connecting the tractor unit 202 and the trailer unit 204 of theworking machine 201. The tractor unit 202 and the trailer unit 204 arepivotally connected to each other for pivoting around a substantiallyvertical pivot axis 213.

The working machine preferably comprises a hydraulic system having twohydraulic cylinders 214, steering cylinders, arranged on opposite sidesof the working machine for turning the working machine by means ofrelative movement of the tractor unit 202 and the trailer unit 204. Thehydraulic cylinders can, however, be replaced by any other linearactuator for steering the machine, such as an electromechanical linearactuator,

Furthermore, the articulated hauler comprises a prime mover 216, hereillustrated as an internal combustion engine, and a gearbox 218 having atransmission arrangement according to the example embodiment describedbelow in relation to FIG. 2. Still further, the articulated hauler alsocomprises a control unit 600 connected to the gearbox for controllingthe below described transmission arrangement. The control unit 600 maybe, or form part of, already existing control Units for controlling agearbox.

Now, with reference to FIG. 2, an example embodiment of a transmissionarrangement 100 according to the present invention is illustrated. Thetransmission arrangement 100 comprises a first planetary gear set 102comprising a sun gear 102S, a planet carrier 102P and a ring gear 102R,a second planetary gear set 104 comprising a sun gear 104S, a planetcarrier 104P and a ring gear 104R, a third planetary gear set 106comprising a sun gear 106S, a planet carrier 106P and a ring gear 106R,and a fourth planetary gear set 108 comprising a sun gear 108S, a planetcarrier 108P and a ring gear 108R. The transmission arrangement 100further comprises an input shaft 136 for receiving a rotarymotion/torque from the prime mover 216 of the vehicle 201 and an outputshaft 112 for providing a rotary motion/torque to the driven wheels ofthe vehicle 201.

The different members of the planetary gear sets 102, 104, 106, 108 ofthe transmission arrangement 100, i.e. the sun gear, the planet carrierand the ring gear, are in the example embodiment depicted in FIG. 2configured according to the following. It should be readily understoodthat the different members described below are connected to each other,either directly, i.e. operatively connected, or via a connectingmechanism, i.e. selectively connectable. The members can be operativelyconnected to each other by means of e.g. a connector element. Suchconnector element can be e.g. a solid shaft, a hollow shaft or a drum,or other suitable element for connecting two members to each other,which elements are known to the person skilled in the art. Hence, noexplicit explanation is given below in regards to the means connectingthe members to each other.

The input shall 136 of the transmission arrangement 100 is operativelyconnected to the ring gear 102R of the first planetary gear set 102,i.e. the input shaft 136 is at all times directly connected to the ringgear 102R of the first planetary gear set 102. The input shaft 136 andthe ring gear 102R of the first planetary gear set 102 are furtherselectively connectable to the ring gear 104R of the second planetarygear set 104 by means of a first connecting mechanism 120. Further, thesun gear 102S of the first planetary gear set 102 is operativelyconnected to the sun gear 104S of the second planetary gear set 104.Also, the sun gear 102S of the first planetary gear set 102 and the sungear 104S of the second planetary gear set 104 are selectivelyconnectable to the ring gear 108R of the fourth planetary gear set 108by means of a third connecting mechanism 124.

Furthermore, the planet carrier 102P of the first planetary gear set 102is selectively connectable to the output shaft 112 by means of a secondconnecting mechanism 122. The planet carrier 102P of the first planetarygear set 102 is also selectively connectable to the ring gear 108R ofthe fourth planetary gear set 108 by means of a fourth connectingmechanism 126.

The planet carrier 104P of the second planetary gear set 104 isoperatively connected to the ring gear 106R of the third planetary gearset 106. Further, the ring gear 104R of the second planetary gear set104 is selectively connectable to the transmission housing 160 by meansof a third locking mechanism 132. Hence, the third locking mechanism132, when being engaged, initially reduces the rotational speed of thering gear 104R of the second planetary gear set 104, and thereafterlocks the ring gear 104R of the second planetary gear set 104 to thetransmission housing 160.

The sun gear 106S of the third planetary gear set 106 is operativelyconnected to the sun gear 108S of the fourth planetary gear set 108.Further, the planet carrier 106P of the third planetary gear set 106 isoperatively connected to the transmission housing 160. Hence, the planetcarrier 106P of the third planetary gear set 106 is at all timesprevented from rotating. Furthermore, the sun gear 106S of the thirdplanetary gear set 106 and the sun gear 108S of the fourth planetarygear set 108 are selectively connectable to the planet carrier 106P ofthe third planetary gear set 106 by means of a second locking mechanism130. Hereby, when engaging the second locking mechanism 130, the sungear 106S of the third planetary gear set 106 and the sun gear 108S ofthe fourth planetary gear set 108 are prevented from rotating since theplanet carrier 106P of the third planetary gear set 106 is operativelyconnected to the transmission housing 160.

The planet carrier 108P of the fourth planetary gear set 108 isoperatively connected to the output shaft 112 of the transmissionarrangement 100. Further, the ring gear 108R of the fourth planetarygear set 108 is selectively connectable to the planet carrier 106P ofthe third planetary gear set 106 by means of a first locking mechanism128. Hereby, when engaging the first locking mechanism 128, the ringgear 108R of the fourth planetary gear set 108 is prevented fromrotating since the planet carder 106P of the third planetary gear set106 is operatively connected to the transmission housing 160.

The above described connecting mechanisms may be respective clutcharrangements which are either wet clutches or dry clutches. The lockingmechanisms may be constituted by brake arrangements such as e.g. wet ordry brake arrangements.

According to the example embodiment depicted in FIG. 2, the stationarygear ratio of each one of the first 102, second 104, third 106, andfourth 108 planetary gear sets are negative. According to a non-limitingexample, the stationary gear ratio for each of the planetary gear setsmay be as described below in Table 1.

TABLE 1 Exemplary stationary gear ratios for the embodiment depicted inFIG. 2. First planetary Second planetary Third planetary Fourthplanetary gear set (102) gear set (104) gear set (106) gear set (108)−1.700 −3.275 −2.075 −2.575

The above described example embodiment depicted in FIG. 2 is adapted toassume the gears as presented in Table 2 below. As indicated, thetransmission arrangement depicted in FIG. 2 assumes nine forward gearsand three reverse gears. In Table 2 below, the locking mechanisms aredenoted simply as “Brakes” while the connecting mechanisms are denotedsimply as “Clutches”. A cell marked with a dot indicates an engagedstate and a blank cell indicates a disengaged state. Furthermore, Table2 also indicates non-limiting examples of the gear ratios and stepsobtainable by the transmission arrangement for the various gears. Thegear ratios and steps presented in Table 2 are derived from theexemplary stationary gear ratios presented in Table 1 above.

TABLE 2 Shift diagram, gear ratios and steps for the different gears.Brakes Clutches Gear 128 130 132 120 122 124 126 Ratio Step 1 ● ● ● 5.921.37 2 ● ● ● 4.33 1.55 3 ● ● ● 2.80 1.27 4 ● ● ● 2.21 1.29 5 ● ● ● 1.711.23 6 ● ● ● 1.39 1.39 7 ● ● ● 1.00 1.30 8 ● ● ● 0.77 1.33 9 ● ● ● 0.58R1 ● ● ● −6.39 1.37 R2 ● ● ● −4.68 2.08 R3 ● ● ● −2.25

As depicted in Table 2 above, the transmission arrangement in FIG. 2comprises nine forward gears and three reverse gears (indicated with anR). The switching of gears can preferably be executed by one-step gearshifts or with two-step gear shifts. One-step gear shift should beunderstood to mean that a gear shift is executed from one gear to thenext coming consecutive gear, for example, gear shift from the firstgear to the second gear, from the second gear to the third gear, fromthe third gear to the second gear, etc. Two-step gear shift should beunderstood to mean that a gear shift is executed to exclude a nextcoming consecutive gear, for example, gear shift from the first gear tothe third gear, from the second gear to the fourth gear, from the thirdgear to the first gear, etc.

As can be seen from Table 2, one-step gear shifting includes only singleshifts of the connecting mechanisms and the locking mechanisms, i.e.when executing one-step gear shifts, only one of the connectingmechanisms/locking mechanisms is shifted from an engaged state to adisengaged state, and only one of the connecting mechanisms/lockingmechanisms is shifted from a disengaged state to an engaged state. As anexample, when shifting from the first forward gear to the second forwardgear, it is only the second connecting mechanism 122 that is changedfrom an engaged state to a disengaged state, and only the fourthconnecting mechanism 126 that is changed from a disengaged state to anengaged state.

Furthermore, and as is depicted in Table 2, also two-step gear shiftingonly includes single shifts of the connecting mechanisms/lockingmechanisms, i.e. when executing two-step gear shifts, only one of theconnecting mechanisms/locking mechanisms is shifted from an engagedstate to a disengaged state, and only one of the connectingmechanisms/locking mechanisms is shifted from a disengaged state to anengaged state. As an example, when shifting from the fourth forward gearto the sixth forward gear, it is only the third locking mechanism 132that is changed from an engaged state to a disengaged state, and onlythe third connecting mechanism 124 that is changed from a disengagedstate to an engaged state.

An advantage of the transmission arrangement is hence that theshiftability is improved since a reduced number of connectingmechanisms/locking mechanisms need activation/deactivation during gearshifting. In detail, during both one-step gear shifting and two-stepgear shifting, which are the most common gear shift sequences, onlysingle shifts occur.

Moreover, with the above described example embodiment of thetransmission arrangement 100, further additional gears are obtainable.Table 3 below illustrates additional gears which are possible to obtainby the transmission arrangement 100 depicted and described above.

In Table 3, gear 0.5* is an additional gear with a gear ratio higherthan the gear ratio of the first forward gear. Also, forward gears 5.5*and 5.5** are additional gears, both having a gear ratio between thegear ratios of the fifth and sixth forward gears. In the following, gear5.5** is referred to as the first additional forward gear. Further,forward gear 10* is a second additional forward gear having a gear ratiolower than the gear ratio of the ninth forward gear, which makes thesecond additional forward gear a faster gear compared to the ninthforward gear.

Furthermore, gears R2.5* and R2.9* are respective first and secondadditional reverse gear each having a gear ratio between the gear ratiosof the second and third reverse gears. Still further, gears R4* and R5*are respective third and fourth additional reverse gears each havinggear ratios lower than the gear ratio of the third reverse gear in termsof absolute values. Hence, the third and fourth additional reverse gearsare faster than the third reverse gear, wherein the fourth additionalreverse gear is faster than the third additional reverse gear.

TABLE 3 Shift diagram, gear ratios and steps for the different gears.Brakes Clutches Gear 128 130 132 120 122 124 126 Ratio Step  0.5* ● ● ●7.15 1.21  1 ● ● ● 5.92 1.37  2 ● ● ● 4.33 1.55  3 ● ● ● 2.80 1.27  4 ●● ● 2.21 1.29  5 ● ● ● 1.71 1.08  5.5* ● ● ● 1.59 1.00  5.5** ● ● ● 1.591.14  6 ● ● ● 1.39 1.39  7 ● ● ● 1.00 1.30  8 ● ● ● 0.77 1.33  9 ● ● ●0.58 1.45 10* ● ● ● 0.40 R1 ● ● ● −6.39 1.37 R2 ● ● ● −4.68 1.55 R2.5* ●● ● −3.02 1.27 R2.9* ● ● ● −2.38 1.06 R3 ● ● ● −2.25 1.31 R4* ● ● ●−1.71 4.04 R5* ● ● ● −0.42

Hence, with the transmission arrangement depicted and described inrelation to FIG. 2, a plurality of additional gears can be achieved. Afurther advantage is thus that the transmission arrangement according tothe present invention has an increased variability when choosing thegears to be used. Thus a plurality of alternatives is possible whendesigning gear shifting of the transmission arrangement.

It is to be understood that the present invention is not limited to theembodiments described above and illustrated in the drawings; rather, theskilled person will recognize that many changes and modifications may bemade within the scope of the appended claims. For example, although thepresent invention has mainly been described in relation to anarticulated hauler, the invention should be understood to be equallyapplicable for any type of vehicle.

The invention claimed is:
 1. A transmission arrangement for a vehicle,the transmission arrangement comprising a first, a second, a third, anda fourth planetary gear set comprising a sun gear, a planet carrier anda ring gear, respectively, wherein the transmission arrangement furthercomprises a transmission housing, an input shaft and an output shaft,wherein the ring gear of the first planetary gear set and the inputshaft are operatively connected to each other; the sun gear of the firstplanetary gear set and the sun gear of the second planetary gear set areoperatively connected to each other; the planet carrier of the secondplanetary gear set and the ring gear of the third planetary gear set areoperatively connected to each other; the planet carrier of the thirdplanetary gear set is operatively connected to the transmission housing;the sun gear of the third planetary gear set and the sun gear of thefourth planetary gear set are operatively connected to each other; andthe planet carrier of the fourth planetary gear set and the output shaftare operatively connected to each other.
 2. The transmission arrangementaccording to claim 1, wherein the transmission arrangement comprises afirst connecting mechanism for selectively connecting the ring gear ofthe second planetary gear set to the ring gear of the first planetarygear set and to the input shaft.
 3. The transmission arrangementaccording to claim 1, wherein the transmission arrangement comprises asecond connecting mechanism for selectively planet carrier of the firstplanetary gear set to the output shaft and to the planet carrier of thefourth planetary gear set.
 4. The transmission arrangement according toclaim 1, wherein the transmission arrangement comprises a thirdconnecting mechanism for selectively connecting the ring gear of thefourth planetary gear set to the sun gear of the first planetary gearset and to the sun gear of the second planetary gear set.
 5. Thetransmission arrangement according to claim 1, wherein the transmissionarrangement comprises a fourth connecting mechanism selectivelyconnecting the planet carrier of the first planetary gear set to thering gear of the fourth planetary gear set.
 6. The transmissionarrangement according to claim 1, wherein the transmission arrangementcomprises a first locking mechanism for selectively locking the ringgear of the fourth planetary gear set to the transmission housing. 7.The transmission arrangement according to claim 6, wherein the ring gearof the fourth planetary gear set is selectively connectable to thetransmission housing via the planet carrier of the third planetary gearset.
 8. The transmission arrangement according to claim 1, wherein thetransmission arrangement comprises a second locking mechanism forselectively locking the sun gear of the third planetary gear set and thesun gear of the fourth planetary gear set to the transmission housing.9. The transmission arrangement according to claim 8, wherein the sungear of the third planetary gear set and the sun gear of the fourthplanetary gear set are selectively connectable to the transmissionhousing via the planet carrier of the third planetary gear set.
 10. Thetransmission arrangement according to claim 1, wherein the transmissionarrangement comprises a third locking mechanism for selectively lockingthe ring gear of the second planetary gear set to the transmissionhousing.
 11. The transmission arrangement according to claim 1, whereinthe stationary gear ratio of each one of the first, second, third andfourth planetary gear sets are negative.
 12. A vehicle comprising aprime mover and a gearbox, wherein the gearbox comprises a transmissionarrangement according to claim
 1. 13. A method for controlling atransmission arrangement, the transmission arrangement comprising afirst, a second, a third, and a fourth planetary gear set comprising asun gear, a planet carrier and a ring gear, respectively, wherein thetransmission arrangement further comprises a transmission housing, aninput shaft and an output shaft, whereby: the ring gear of the firstplanetary gear set being operatively connected to the input shaft; thesun gear of the first planetary gear set being operatively connected tothe sun gear of the second planetary gear set; the planet carrier of thesecond planetary gear set being operatively connected to the ring gear(106R) of the third planetary gear set; the planet carrier of the thirdplanetary gear set being operatively connected to the transmissionhousing; the sun gear of the third planetary gear set being operativelyconnected to the sun gear of the fourth planetary gear set; the planetcarrier of the fourth planetary gear set being operatively connected tothe output shaft, wherein the transmission arrangement furthercomprises: a first connecting mechanism for selectively connecting thering gear of the second planetary gear set to the ring gear of the firstplanetary gear set and to the input shaft; a second connecting mechanismfor selectively connecting the planet carrier of the first planetarygear set to the output shaft and to the planet carrier of the fourthplanetary gear set; a third connecting mechanism for selectivelyconnecting the ring gear of the fourth planetary gear set to the sungear of the first planetary gear set and to the sun gear of the secondplanetary gear set; a fourth connecting mechanism for selectivelyconnecting the planet carrier of the first planetary gear set to thering gear of the fourth planetary gear set; a first locking mechanismfor selectively locking the ring gear of the fourth planetary gear setto the transmission housing; a second locking mechanism for selectivelylocking the sun gear of the third planetary gear set and the sun gear ofthe fourth planetary gear set to the transmission housing; and a thirdlocking mechanism for selectively locking the ring gear of the secondplanetary gear set to the transmission housing, wherein for at least oneof the gears of the transmission arrangement, the method comprises thesteps of: positioning three of the locking and connecting mechanisms inan engaged state; and positioning four of the locking and connectingmechanisms in a disengaged state.
 14. A control unit configured tocontrol a transmission arrangement, the transmission arrangementcomprising a first, a second, a third, and a fourth planetary gear setcomprising a sun gear, a planet carrier and a ring gear, respectively,wherein the transmission arrangement further comprises a transmissionhousing, an input shaft and an output shaft, wherein: the ring gear ofthe first planetary gear set being operatively connected to the inputshaft; the sun gear of the first planetary gear set being operativelyconnected to the sun gear of the second planetary gear set; the planetcarrier of the second planetary gear set being operatively connected tothe ring gear (106R) of the third planetary gear set; the planet carrierof the third planetary gear set being operatively connected to thetransmission housing; the sun gear of the third planetary gear set beingoperatively connected to the sun gear of the fourth planetary gear set;the planet carrier of the fourth planetary gear set being operativelyconnected to the output shaft, wherein the transmission arrangementfurther comprises: a first connecting mechanism for selectivelyconnecting the ring gear of the second planetary gear set to the ringgear of the first planetary gear set and to the input shaft; a secondconnecting mechanism for selectively connecting the planet carrier ofthe first planetary gear set to the output shaft and to the planetcarrier of the fourth planetary gear set; a third connecting mechanismfor selectively connecting the ring gear of the fourth planetary gearset to the sun gear of the first planetary gear set and to the sun gearof the second planetary gear set; a fourth connecting mechanism forselectively connecting the planet carrier of the first planetary gearset to the ring gear of the fourth planetary gear set; a first lockingmechanism for selectively locking the ring gear of the fourth planetarygear set to the transmission housing; a second locking mechanism forselectively locking the sun gear of the third planetary gear set and thesun gear of the fourth planetary gear set to the transmission housing;and a third locking mechanism for selectively locking the ring gear ofthe second planetary gear set to the transmission housing, wherein forat least one of the gears of the transmission arrangement, the controlunit (600) is configured to: position three of the locking andconnecting mechanisms in an engaged state; and position four of thelocking and connecting mechanisms in a disengaged state.